package com.company.Algorihm;

import java.lang.reflect.Array;
import java.util.Arrays;

/**
 * @author VX5
 * @Title: MJC
 * @ProjectName DataStructure
 * @Description: TODO
 * @date ${DAT}20:05
 */
public class FloydAlgorithm {
    public static void main(String[] args) {
        char[] vertex = { 'A', 'B', 'C', 'D', 'E', 'F', 'G' };
        //创建邻接矩阵
        int[][] matrix = new int[vertex.length][vertex.length];
        final int N = 65535;
        matrix[0] = new int[] { 0, 5, 7, N, N, N, 2 };
        matrix[1] = new int[] { 5, 0, N, 9, N, N, 3 };
        matrix[2] = new int[] { 7, N, 0, N, 8, N, N };
        matrix[3] = new int[] { N, 9, N, 0, N, 4, N };
        matrix[4] = new int[] { N, N, 8, N, 0, 5, 4 };
        matrix[5] = new int[] { N, N, N, 4, 5, 0, 6 };
        matrix[6] = new int[] { 2, 3, N, N, 4, 6, 0 };
        //创建 Graph 对象
        Graph graph = new Graph(vertex.length, matrix, vertex);
        graph.floyd();
        graph.show();
    }

    static class Graph{
        private char[] vertex;
        private int[][] dis;//保存，从各个顶点出发到其他顶点的距离，最后的结果，也是保留在该数组
        private int[][] pre;//保存到达目标顶点的前驱顶点

        //构造器

        /**
         *
         * @param length
         * @param matrix
         * @param vertex 顶点数组
         */
        public Graph(int length,int[][] matrix,/*邻接表*/char[] vertex){
            this.vertex = vertex;
            this.dis = matrix;
            this.pre = new int[length][length];//存放的是前驱顶点的下标
            for (int i = 0; i < length;i++){
                Arrays.fill(pre[i],i);//复制一行
            }
        }

        //显示pre数组和dis数组
        public void show(){
            for (int k = 0;k < dis.length;k++){
                //先将pre输出
                for (int i = 0;i < dis.length;i++){
                    System.out.print(vertex[pre[k][i]] + " ");
                }
                System.out.println();
                for (int j = 0;j < dis.length;j++){
                    System.out.print(vertex[k]+"到"+vertex[j]+":"+dis[k][j]+" ");
                }
                System.out.println();
            }
        }

        public void floyd(){
            int len = 0;
            for (int k = 0; k < dis.length;k++){
                for (int i = 0; i < dis.length;i++){
                    for (int j = 0; j< dis.length;j++){
                        len = dis[i][k] + dis[k][j];//k为中间点
                        if (len<dis[i][j]){//小于直连才是最小
                            dis[i][j] = len;
                            pre[i][j] = pre[k][j];
                        }
                    }
                }
            }
        }
    }
}
